Long term evolution (“LTE”) of the Third Generation Partnership Project (“3GPP”), also referred to as 3GPP LTE, refers to research and development involving the 3GPP LTE Release 8 and beyond, which is the name generally used to describe an ongoing effort across the industry aimed at identifying technologies and capabilities that can improve systems such as the universal mobile telecommunication system (“UMTS”). The notation “LTE-A” is generally used in the industry to refer to further advancements in LTE. The goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards.
The evolved universal terrestrial radio access network (“E-UTRAN”) in 3GPP includes base stations providing user plane (including packet data convergence protocol/radio link control/medium access control/physical (“PDCP/RLC/MAC/PHY”) sublayers) and control plane (including radio resource control (“RRC”) sublayer) protocol terminations towards wireless communication devices such as cellular telephones. A wireless communication device or terminal is generally known as user equipment (also referred to as “UE”). A base station is an entity of a communication network often referred to as a Node B or an NB. Particularly in the E-UTRAN, an “evolved” base station is referred to as an eNodeB or an eNB. For details about the overall architecture of the E-UTRAN, see 3GPP Technical Specification (“TS”) 36.300 v8.7.0 (2008-12), which is incorporated herein by reference. For details of the radio resource control management, see 3GPP TS 25.331 v.9.1.0 (2009-12) and 3 GPP TS 36.331 v.9.1.0 (2009-12), which are incorporated herein by reference.
As wireless communication systems such as cellular telephone, satellite, and microwave communication systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communication devices that transmit an increasing quantity of data within a fixed spectral allocation and limited transmit power. The increased quantity of data is a consequence of wireless communication devices transmitting video information and surfing the Internet as well as performing ordinary voice communication. To address these ongoing needs, a current topic of general interest in 3GPP is the efficient use of spatially multiplexed cellular transmission. The efficient use of spatially multiplexed transmission can enable a higher data rate to be transmitted per hertz (“Hz”) of bandwidth at a limited transmit power level, thereby enabling a larger amount of data to be transmitted by a wireless communication device in a shorter period of time, or, equivalently, accommodation of substantially simultaneous operation of a larger number of wireless communication devices.
In order to meet peak spectral efficiency requirements (up to 30 bit(s)/Hz), support of up to eight transmit (“Tx”) antennas in a downlink (“DL”) will be standardized in 3GPP LTE Rel-10, enabling downlink spatially multiplexed transmission with up to eight spatial layers. Both eight-transmit downlink multi-input/multi-output (“MIMO”) and enhanced multi-user multi-input/multi-output (“MU-MIMO”) are now agreed to be part of a Rel-10 work item on enhanced downlink MIMO transmission. Such processes will enable the higher data rate to be transmitted with a limited transmitter power level per hertz of bandwidth.
The processes, however, to enable a wireless communication device to communicate channel state and other related information back to a base station so that spatially multiplexed transmission in a downlink can be efficiently performed by the base station introduces a number of challenges. One of the more problematic issues is how to how to deal with the increased communication channel dimensionality and degrees of freedom associated with downlink antenna beam formation (also known as transmit precoding) without channel state information reporting burdening the uplink communication channel for the wireless communication device. Another issue is enabling improved single-user multi-input/multi-output (“SU-MIMO”) performance with large azimuthal spread in the wireless communication channel at the transmit antenna array. It is generally recognized that coverage for wireless communication devices located at the crossing of beams in the antenna beam space can be poor with present arrangements.
In view of the growing deployment of communication systems such as cellular communication systems and these unresolved issues, it would be beneficial to employ an improved codebook format to enable a wireless communication device to efficiently determine and communicate channel state and antenna beam characteristics to a base station that avoids the deficiencies of the current communication systems.